Alkoxylated, inorganic phosphorus acid free, steam hydrolyzed polyalkene-P.sub.2 S.sub.5 reaction products hereinafter also referred to as the alkoxylated product have long been known as superior detergent-dispersants in lubricating oils. The standard method of preparation of these alkoxylated products is first reacting a polyalkene with P.sub.2 S.sub.5 to form the polyalkene-P.sub.2 S.sub.5 reaction product, this reaction preferably conducted in the presence of a catalytic amount of sulfur, e.g., between about 0.1 and 1 wt. % to facilitate the reaction. The resultant reaction product is then hydrolyzed with steam followed by the removal of formed inorganic phosphorus acid by-products therefrom. The steam hydrolyzed inorganic phosphorus acid free polyalkene-P.sub.2 S.sub.5 reaction product is then alkoxylated to form the alkoxylated product. In the absence of inorganic acid the alkoxylation results in essentially a monoalkoxylated as opposed to a polyalkoxylated product. This resultant product has been characterized in the past by the formula: ##EQU1## where R is hydrocarbyl and R.sup.1 and R.sup.2 are hydrogen or alkyl. Since the product in essence is a complex mixture of many compounds including ring compounds containing phosphorus and sulfur in the ring as well as phosphoric and thiophosphoric structures, definition of the product in terms of process appears suitable.
Although these prior alkoxylated products are excellent detergent-dispersants, they have been evidencing some undesirable properties when utilized in the recently developed high temperature automotive engines fitted with anti-pollution devices. Specifically, under the aforementioned conditions they appear to contribute to the sometimes substantial increase of lubricant compositions containing same. Investigation has determined that this undesired oil thickening is partially the result of the oxidative breakdown of the alkoxylated detergent-dispersant triggered by excessibly high engine temperature coupled with the funneling of ever increasing amounts of engine exhaust into the crankcase for anti-pollution treatment. One means of counteracting this oxidative tendency was to include antioxidants in the lube formulations such as the alkylated diphenylamines. Although the added antioxidants successfully retarded the oxidative decomposition of the alkoxylated product, they have the undesired feature of contributing to the excessive quantities of additives required in modern day engine oils as well as being another factor adding to the cost of said oils.
Another ever present problem with the alkoxylated products is the harsh sulfurous odor evolving in the initial use of lubricating compositions containing said alkoxylated products. This odor is believed caused by the evolution of volatile sulfurous materials loosely held in a chemical sense in the reaction product. In the past, one means of removing these objectionable odors was to blow the products with nitrogen dioxide; however, such treatment places an undesirable burden on the manufacturing facilities in respect to control of the exiting nitrogen oxides in order to avoid atmospheric pollution.
Accordingly, objects of this invention are to provide a method to produce a detergent-dispersant alkoxylated product of improved odor which is resistant to oxidative breakdowns in engine operation caused by the strains of high temperature and anti-pollution devices placed on lubricating oils containing said alkoxylated product.
Another object is to provide a detergent-dispersant alkoxylated product of improved odor and oxidation resistant properties and lubricating oil compositions thereof.